Bird Flu Jumps to Seals, Humans Could Be Next

NEW YORK, New York, August 6, 2012 (ENS) – A bird flu virus known for 10 years has now infected aquatic mammals, and the scientists who discovered the source of the infection are warning that the virus could become a public health threat.

The virus, known as avian H3N8 influenza A, was responsible for an outbreak of fatal pneumonia that has infected harbor seals in New England, a scientific team has found. The death of these seals is a U.S. federally recognized “unusual mortality event.“

The discovery of the connection between the bird flu virus and the seal deaths was made by a team of scientists from the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health, the National Oceanic and Atmospheric Association, the New England Aquarium, the U.S. Geological Survey’s National Wildlife Health Center, SeaWorld and the EcoHealth Alliance.

“This outbreak is particularly significant, not only because of the disease it caused in seals but also because the virus has naturally acquired mutations that are known to increase transmissibility and virulence in mammals,” the scientists write in the current issue of “mBio,” a journal published by the American Society for Microbiology.

Wildlife officials first became concerned in September 2011, when seals with severe pneumonia and skin lesions suddenly appeared along the coastline from southern Maine to northern Massachusetts. Most were younger than six months of age, and a total of 162 dead or moribund seals were recovered over the next three months.

Analysis of postmortem samples revealed the presence of an avian H3N8 influenza A virus. “This pathogen is similar to a virus circulating in North American waterfowl since at least 2002 but with mutations that indicate recent adaption to mammalian hosts,” the scientists write.

“When initial tests revealed an avian influenza virus, we asked the obvious question – how did this virus jump from birds to seals?” says Simon Anthony, a postdoctoral research scientist at the Center for Infection and Immunity and the lead author of the study.

Testing and analysis shows that the virus, now called seal H3N8, has acquired the ability to bind to receptors that are commonly found in the respiratory tracts of mammals, including humans.

The scientists warn that seal H3N8 could pose a threat to public health, given these findings along with the long history of the spread of avian influenza to humans.

The first bird flu virus to infect humans occurred in Hong Kong in 1997. The epidemic was linked to chickens and classified as avian influenza A, strain H5N1. Human cases of H5N1 infection have since been reported in Asia, Africa, Europe, Indonesia, Vietnam and the Pacific. Hundreds of people have become sick with this virus, more than 60 percent of those infected have died.

A different bird flu strain, the H1N1 flu virus, caused a worldwide pandemic in 2009. Although the World Health Organization announced the pandemic was over in August 2010, H1N1, commonly called swine flu, is still circulating.

“The emergence of new strains of influenza virus is always of great public concern,” the scientists write in their study, “especially when the infection of a new mammalian host has the potential to result in a widespread outbreak of disease.”

“Our findings reinforce the importance of wildlife surveillance in predicting and preventing pandemics, says W. Ian Lipkin, director of the Center for Infection and Immunity and John Snow Professor of Epidemiology, at the Mailman School of Public Health.

“HIV/AIDS, SARS, West Nile, Nipah and influenza are all examples of emerging infectious diseases that originated in animals,” said Lipkin.

Lipkin said, “Any outbreak of disease in domestic animals or wildlife, while an immediate threat to wildlife conservation, must also be considered potentially hazardous to humans.”

The editor of the report, Anne Moscona of Weill Cornell Medical College in New York City, says it raises two concerns about flu. First, this strain is a novel virus that infects mammals and may well pass from animal to animal, a combination of traits that make it a potential threat to humans.

“There is a concern that we have a new mammalian-transmissible virus to which humans haven’t been exposed yet. It’s a combination we haven’t seen in disease before,” Moscona says.

Also, says Moscona, the possibility that a bird flu virus would infect seals had not been widely considered before, highlighting the fact that flu pandemics can appear in unexpected ways.

Moscona emphasizes the need for readiness. “Flu could emerge from anywhere and our readiness has to be much better than we previously realized. We need to be very nimble in our ability to identify and understand the potential risks posed by new viruses emerging from unexpected sources.”